Strain of an object is defined as:

 is the final length and  is the initial length. The equation implies that increasing the initial length of an object () would decrease the strain. Similarly, the equation also implies that increasing the final length of an object () would increase the strain; therefore, increasing the initial length decreases strain, whereas increasing the final length increases strain.

To answer this question, we need to know the equation for Young’s modulus, :

Recall the definitions of stress and strain:

Here,  is force,  is cross-sectional area,  is change in length, and  is initial length. Plugging these two equations into the definition of Young’s modulus gives us:

Rearranging this equation to solve for change in length gives us:

Since we want to increase  we look for answer choices that increase  and , or decrease  and . Among the answer choices, the greatest increase occurs when you double the elasticity of the rubber band. Recall that Young’s modulus is a measure of the stiffness of a material; therefore, a more elastic (flexible, or less stiff) material will lower Young’s modulus. Having a material twice as elastic will decrease  by one half and will give the greatest increase in the change in length of the rubber band. 

Using half the length () and using twice the cross-sectional area will decrease the change in length. Using a rubber band twice as long, but twice as elastic, will not alter the change in length.

Young’s modulus is a constant that is calculated by generating a stress vs. strain plot. The slope of the linear region of the stress vs. strain plot is defined as the Young’s modulus. Recall that the stress vs. strain plot is nonlinear past the elastic limit (stress at which the material starts to plastically deform). This means that we cannot calculate the slope past the elastic limit; Young’s modulus is invalid for stresses beyond the elastic limit.

Young’s modulus is defined as follows:

To calculate strain, you divide change in length by initial length. Since both change in length and initial length have the same units, the units cancel and strain becomes a dimensionless quantity. This means that the Young’s modulus will have the same units as stress alone. 

Young’s modulus is a material property. This means that the Young’s modulus is constant for a given type of material. It does not depend on the stress experienced by the material. Any changes to stress will be compensated for by a change in strain, which will allow Young’s modulus to be constant for the material. Similarly, Young’s modulus does not depend on strain or on the geometrical properties (length and area) of the material. It will only change if you change the type of material being used.

Compounds with an alcohol group show absorptions in an IR sprectrum from  through . Therefore an absorption of  would correspond to an alcohol. Amide groups show absorptions from  through . Amine groups show absorptions from  through , through ,  through  and  through  (aromatic amines). Carbonyl compounds such as aldehydes show strong absorptions in the IR spectrum at  through .

Distillation is a process of separating a liquid from solutes or other liquids. It utilizes the boiling point differences to separate substances. A substance with a low boiling point will evaporate first in a distillation column and will be isolated first. The question is asking which solution will be isolated first; therefore, we need to figure out which solution has the lowest boiling point. Recall that the boiling point of a solution is elevated when there are more solutes present in the solution. Sodium chloride () contributes two solutes (sodium ions and chloride ions). Calcium nitrate () contributes three solutes (one calcium ion and two nitrate ions). Sucrose does not dissociate into ions in solution; therefore, it only contributes one solute. This means that the sucrose solution will have the lowest amount of molecules in solution, the lowest boiling point, and will be separated first.

There are two types of distillation. Simple distillation is used to separate molecules that have very different boiling points. Fractional distillation is used to separate molecules with small differences in boiling points. Fractional distillation is often used if the difference between boiling points is less than . In simple distillation, the vapor is immediately collected in a condenser. On the other hand, fractional distillation allows vapor to condense and revaporize several times. These repeated cycles allow fractional distillation to purify the vapor better than simple distillation.

Distillation is used to separate molecules with different boiling points. Simple distillation is used to separate molecules with vastly different boiling points. Fractional distillation, on the other hand, is a refined form of simple distillation that can be used to separate molecules with similar boiling points. Note that fractional distillation can separate molecules with either different or similar boiling points; therefore, fractional distillation can be used to separate any of the given mixtures. 

Rate of distillation is increased when the ability of a substance to become a vapor is increased. Recall that vapor is created when enough heat is applied to the liquid. The temperature at which the liquid becomes vapor is called the boiling point. A liquid turns into a vapor when the vapor pressure (pressure applied by the vapor from the liquid) equals the atmospheric pressure. Decreasing the atmospheric pressure will make it easier for the liquid to turn into a vapor; therefore, this will increase the rate of distillation.

Decreasing the vapor pressure will remove vapor from system. This will make it harder to distill substances. Decreasing temperature will move the system away from the boiling point, thereby decreasing the amount of vapor. Decreasing mole fraction of the substance will decrease the surface area of the substance (at the surface of the solution). Liquid molecules need to be present at the surface to escape the solution and become vapor; therefore, decreasing mole fraction will decrease the amount of vapor.

TLC is a laboratory technique commonly used to separate components of a mixture. Mixtures are placed on the TLC plate (stationary phase), which is then transferred to a jar containing the solvent. The solvent travels through the plate and carries components of the mixture along with it. Based on its properties, each component is dragged to different distances on the plate. The relative distances travelled by each component can be used for separation and identification.

It is important to place a lid on the jar because the solvent will be a volatile substance. An open system will allow for the solvent to evaporate from the TLC plate and reduce the amount of solvent travelling through the plate. The solvent in the solution will evaporate, but it is negligible and inconsequential to the data collected on the TLC plate. 

Thin layer chromatography (TLC) is used to separate components in a mixture. Components are separated on a TLC plate because each component travels a different distance. The distance travelled depends on several factors. One of those factors is polarity; therefore, TLC can used to determine polarity of substances.

TLC is not useful for identifying substances. Other techniques such as NMR and IR spectroscopy are useful for identifying individual components. The R_f value of a compound can help identify it in a broad sense, but this technique provides only very rudimentary identification capabilities.